Take-down assembly for a firearm with a gas piston



Oct. 10, 1961 J. H. JOHNSON 3,003,400

TAKE-DOWN ASSEMBLY FOR A FIREARM WITH A GAS PISTON Filed Jan. 21, 1960 2Sheets-Sheet 1 IN VEN TOR. JAMES H. JOHNSON Fa m v n. h v I r TAKE-DOWNASSEMBLY FOR A FIREARM WITH A GAS PISTON Filed Jan. 21, 1960 Oct. 10,1961 J. H. JOHNSON 2 Sheets-Sheet 2 INVENTOR JAMES H. JOHNSON UnitedStates Patent 3,003,400 TAKE-DOWN ASSEMBLY FOR A FIREARM WITH A GASPISTON James H. Johnson, New Haven, Conn., assignor to 01m MathiesonChemical Corporation, a corporation of Filed Jan. 21, 1960, Ser. No.3,776 6 Claims. (Cl. 89-191) The present invention relates to firearmsand in particular to a novel assembly which facilitates take-down.

The invention is also related to a novel method for assembling andtaking down a firearm.

As is traditional in the art, the terminology takedown is intended torefer'to disassembly including the method of disassembly for purposes ofcleaning, oiling and repair.

Among the features of the invention is the provision of a firearm havinga forearm wherein the forearm is rigidly connected to the barrel only atthe forward end thereby permitting the after or rear end of the forearmto come and go or seat itself axially as necessary and as conditions ofatmosphere and climate affect expansion and contraction of metallic andwooden parts.

Another feature of the invention is the provision of a firearm having asimple take-down assembly in which there is a minimum of close tolerancepiece parts.

A further feature of the invention is the provision of a take-downassembly in a gas operated firearm in which a centrally disposed guiderod is utilized to carry a working piston and track means for the boltwhere the track means are formed with connector means for receiving andretaining the rear end of the forearm.

A further feature of the invention is the provision of a firearmtake-down assembly wherein there is unusual cooperation between thetrigger assembly, bolt, working piston, piston cylinder, and theforearm.

A firearm including certain principles of the present invention andembracing the special take-down assembly and take-down method maycomprise a forearm, a barrel, a receiver having a bore, a triggerassembly secured to the receiver and having a track means for slidablysupporting a bolt, a bracket carried by the barrel apertured to define acylinder and to receive slidably a guide rod, a working piston withinthe cylinder and carried by the rod having operating means connected tothe bolt for actuating the bolt along the track means when the piston isdriven, connector means formed integral with the track means andsupported by the guide rod for engaging and retaining one end of theforearm, and screw means engaging the bracket and the forearm forrigidly securing the opposite end of the forearm to the barrel.

Other features and advantages of the present invention will become moreapparent-fre mthe-saeeeeding speefi cation when read in conjunction withthe appended drawings, in which:

FIG. 1 is an elevational view of a gas operated firearm embracing theprinciples of the present invention with certain portions broken awayfor clarity;

FIG. 2 is a continuation of the right end of the representation of FIG.1;

FIG. 3 is a vertical section of the drawing of FIG. 1 taken along thezig zag line 3-3;

FIG. 4 is a further section of FIG. 1 taken in the plane of the line4-4;

FIG. 5 is a section of FIG. 2 in the plane of the line 5-5, and,

FIG. 6 is a perspective view of the track means and the connector meansboth of which are integral parts of the trigger assembly of FIG. 1.

3,003,400 Patented Oct. 10, 1961 Referring now in detail to thedrawings, there is shown a barrel 10 having a depending bracket 11formed with a first bore 12 defining a cylinder or a compressionchamber. The bore 12 communicates with the interior 5 of the barrel 10by means of the passageway 13 in well known fashion whereby gasdeveloped in the barrel may flow into the compression chamber tointroduce kinetic energy to a piston 14 slidably carried upon a movablymounted guide rod '16. One end of the rod 16 is slid- 10 ably receivedin a second bore 17 formed in the bracket;

the other end is slidably received in a bore 18 formed in a receiver 19.

The working piston 14 operates a pair of bolt actuating arms 21-21connected to the piston at their forward end by means of a U-shapedstrap 22 having a central tongue 24. The opposite or rear ends of theoperating arms 21-21 engage the bolt wherein a generally saddleshapedbridge element 26 formed integral with the arms is received in a cut outportion 27 of a bolt means 28 as is most apparent in FIG. 1. I

Note that the trigger assembly, indicated generally by the referencenumeral 29, includes a track means '31 (FIG. 6) and a connector means 32comprising a pair of spaced, parallel rails 33-3-3 joined'by a U-shapedbridge 34 and having an upstanding ear 36 apertured at 35 and a pair offorwardly projecting fingers 37-37. The rails 33-33 are connected to atrigger guard 15 by means of a rivet 2 0. 1

As is apparent in FIGS. 1 and 2, a forearm, indicated generally at 38,cooperates with the barrel and the receiver to surround and enclose theguide rod 16, the piston and the bolt operating arms 21-21. 1

Note :that the after end of the forearm slidably receives the projectingfingers 37-37 of the connector means 32 and a portion of the bridge 34so that, in

effect, the rear end of the forearm does not abut the receiver but isfree to float, axially, as normal expansion and contraction occurs.

It is further noted that the rear end of the forearm is provided with apair of horizontally disposed, spaced undercut slots 40-40 to receivethe fingers 37-37 thereby precluding the after portion of the forearmfrom dropping downwardly away from the receiver after assembly. Incontrast, the forward end of the forearm is rigidly connected to thefirearm through the bracket 11 wherein a screw means characterized by ascrew 39 threadedly engages the bracket and passes through an apertureformed in the forearm to fix this end of the forearm rigidly in abutmentwith the bracket.

To avoid close tolerance dimensions governing the length of the guiderod 16, the bore 18 is partially filled with a coil spring 41 whichconstantly urges the rod to the right into abutment with the screw 39.In this ar rangement there is no danger that the rod 16 will bottom -andthereforen'nterfere before the screw iiibrings the forward end of theforearm into rigid abutment with the bracket 11.

In operation, introduction of gas pressure into the pres sure cavity 12introduces kinetic energy to the working piston 14 operative through theoperating arms 21 to drive the bolt rearwardly along the track means orrails 33-33 of the trigger assembly. A return spring 42 operates toreturn the working piston to its normal position.

To take down the firearm, it is simply necessary to remove the screw 39whereupon the forearm is free to move to the right as viewed in FIGS. 1and 2 off the bracket 11 while the rear portion of the forearm slides01f the fingers 37-37 and off the bridge 34 quickly exposing theinterior of the action.

Since the rod 16 is slidably disposed, it is readily withdrawn,releasing the springs 41 and 42.

Thereafter pin 43 is removed releasing the trigger assembly includingthe track means 31 and the connector means 32 from the receiver 19. Apin 25 carried by the rails 33-33 provides a pivotal mounting for ahammer (.not shown). The bolt means drops downwardly out of the receiverwhile the piston assembly including the operating arms 21-21 is movedslightly to the left as viewed in FIG. 2 to Withdraw it from thecylinder and thereafter drops downward freely.

It is anticipated that a variety of modifications and design changes maybe devised in the disclosed embodiment of the invention withoutdeparting from the spirit and scope of the invention.

What is claimed is:

1. In combination in a firearm a barrel, a receiver, a guide rod movablysupported by the barrel and the receiver, a bolt actuating pistoncarried by the rod, a trigger assembly carried by the receiver and therod and a forearm cooperating with the barrel to enclose the piston andthe rod, said forearm being carried by the barrel and the triggerassembly.

2. In a firearm the combination of a forearm, a guide rod, a bolt, 2.barrel, a receiver having a bore, a trigger assembly including trackmeans for slidably supporting the bolt and a connector means forsupporting the forearm, a bracket carried by the barrel apertured toreceive slidably the guide rod, one end of said rod being received insaid bore, a working piston within the bracket carried by said guide rodand having operating means connected to the bolt for actuating the boltalong the track means when the piston is driven, said connector meansbeing formed integral with the track means and supported by the guiderod for engaging and retaining one end of the forearm, and screw meansengaging the bracket and the forearm for rigidly securing the oppositeend of the forearm to the barrel.

3. A take-down assembly for a gas operated firearm comprising a barrel,a guide rod, a trigger assembly, a

receiver having a bore, a bracket carried by the barrel apertured toslidably receive the guide rod, a piston carried by one end of the guiderod, the opposite end of the guide rod being received in the bore, saidpiston cooperating with said bracket to define a compression chamber,resilient means in the bore and in series with the guide rod for urgingthe guide rod toward said bracket, screw means engageable with saidbracket and said one end of the guide rod operative to fasten a forearmto the barrel rigidly, said screw means being further operative to drivesaid guide rod in a direction which tends to compress the spring topreclude jamming, the opposite end of said guide rod being operative tocarry one end of the trigger assembly, said trigger assembly terminatingin a pair of fingers operative to project, in telescoping fashion, intothe rear of the forearm whereby the forearm fully encloses the guiderod.

4. In a firearm of the class having a guide rod, a barrel, a receiverand a trigger assembly, the combination therewith of means for movablysuspending the guide rod from the receiver and from the barrel, a boltactuating piston carried by the rod, means for securing the triggerassembly to the receiver and to the rod and a forearm fastened to thebarrel and to the trigger assembly for enclosing the rod.

5. The firearm of claim 4 wherein the means for suspending the rod is abracket having a cylindrical bore which communicates with the interiorof the barrel.

6. The firearm of claim 4 wherein the trigger assembly includes trackmeans for guiding a bolt and connector means for receiving one end ofthe forearm telescopically.

References Cited in the file of this patent UNITED STATES PATENTS2,685,754 Crittendon et ah Aug. 10, 1954

